1. Field of the Invention
The present invention relates to a lighting system and a projection system which have an improved structure, so that the lighting system and the projection system can be made small and thin.
2. Description of the Related Art
Techniques for making projection systems small and thin have been researched and developed. In the conventional art, techniques for making a projection system small include using a mirror method and a total reflection prism. In particular, a technique using the mirror method is applied to make a projection system small and lightweight.
An image displaying apparatus using the mirror method is disclosed in Japanese Patent Publication No. 2000-98272. Here, as shown in FIGS. 1 and 2, in the image displaying apparatus, light emitted from a light source 100 is split into R, G, and B color beams by a color wheel filter 103. The R, G, and B color beams are sequentially reflected on a first reflecting mirror 105. Next, the R, G, and B color beams are reflected on a second reflecting mirror 107, and then focused onto a deformable mirror device (DMD) 110. A condenser lens 104 is further included in an optical path between the color wheel filter 103 and the first reflecting mirror 105.
The DMD 110 has a plurality of micromirrors (not shown), which are two-dimensionally arranged and turned on and off according to an image signal input to each pixel. When the micromirrors are turned on, light reflected on the micromirrors is incident on a projection lens unit 113. When the micromirrors are turned off, light reflected on the micromirros travel in a direction deviating from the projection lens unit 113. Thus, R, G, and B color beams are incident or not incident on pixels each corresponding to the R, G, and B color beams to form a color image.
With reference to FIG. 1, light emitted from the light source 100 passes through the first reflecting mirror 105 and the second reflecting mirror 107 to the DMD 110. In the above-described structure, the first reflecting mirror 105, the second reflecting mirror 107, and the DMD 110 are arranged in a triangle shape. The projection lens unit 113 is installed aside the second reflecting mirror 107. However, the projection lens unit 113 is arranged in a proper position so that light reflected from the DMD 110 is incident on the projection lens unit 113. In a conventional optical path, the first reflecting mirror 105, the second reflecting mirror 107, and the DMD 110 are arranged in different directions and different positions, respectively. Thus, an image displaying apparatus cannot be made small.
Light reflected from the first reflecting mirror 105 is incident on the second reflecting mirror 107, which is disposed in a different position from the first reflecting mirror 105. Light reflected from the second reflecting mirror 107 is incident on the DMD 110 opposite to the second reflecting mirror 107. Thus, the optical path is complicated. Therefore, when a DMD installed in a narrow space is turned on/off, it is difficult to split a beam according to a method of driving pixels processing image data in the DMD. Also, when the DMD is turned off, light may be incident on the projection lens unit 113. Moreover, since the second reflecting mirror 107 and the projection lens unit 113 are arranged in the same direction, an installation space is considerably limited.